Transfer molding press



March 22, 1949. H. w. DALTON TRANSFER MQLIDING PRESS Filed Nov. 6, 1947 4 23 4 w W 23 V 4 \g 3 v at? 5; I 5

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Y. INVENTOR HERBERT WILLIAM DALTON,

ATTORNEY Patented Mar. 22, 1949 TRANSFER MOLDING PRESS Herbert William Dalton, Redfern, New South Wales, Australia Application November 6, 1947, Serial No. 784,351 In Australia November 7, 1946 1 Claim.

This invention relates to moulding presses, and has particular reference to presses for forming mouldings from powders (plastic mouldings) by the transfer (injection) process, The press could be possibly adapted to other pressure mouldings, for instance, metal pressure mouldings.

In presses for this purpose it is conventional practice to employ a separate plunger to inject the powder charge (usually in tablet form) into the die after the two halves of the die have been closed. This separate plunger is operated independently from the operation of the ram or rams operating the die, and hence calls for separate manipulation by the operator, and probably loss of time in each moulding, both of which are matters of consequence when many thousands of an articles are being formed in succession.

Furthermore, such conventional system permits of operation of the injection plunger before the die is closed, with the result that the moulding is spoilt.

The object of this invention is to provide a press in which the injection plunger is operated automatically (without manipulation by the operator) immediately after the die has closed. This prevents the spoiling of a moulding, saves time in that the injection is efiected as soon as the die has closed, and relieves the operator of the necessity for separately operating the injection plunger.

The injection plunger is operated by the same hydraulic pressure which operates the main die rams.

In order to fully describe the invention reference is made to the accompanying drawings, which depict a preferred embodiment of the press, and in which Fig. 1 is a vertical cross-section of the press with the die in open position, and

Fig. 2 is an elevation of the press partly in cross-section, taken at right angles to Fig. 1, with the die in closed position after an injection.

The drawings omit conventional ancillary equipment used in such presses such as the external hydraulic control mechanism.

The press comprises the conventional base 3, upper head 4 secured to the base by four standards 5, upper die section 6 secured to up r head 4, and lower die section 7 which is vertically reciprocable under hydraulic power from the open position shown in Fig. 1 to the closed position shown in Fig. 2. The two halves of the moulding recess are conventionally illustrated at 8' in the lower die section, and at 8 in the upper die section. The die sections are provided with the conventional locating pins 9' which engage in recesses 9 Lower die section 1 is secured on a base Ill which is seated upon two spaced blocks II, II in turn seated upon a die platen l2 secured to the upper end of a main closing ram l3 vertically reciprocable through base 3 and entering a pressure cylinder M therein. Thus hydraulic pressure admitted to cylinder I 4 will be transmitted by ram l3, platen 12, blocks II, and die base I 0, to the lower die section 1.

Lower die section I and base ID are provided with a cylindrical base Hi to receive a vertically reciprocable injection plunger l6 which is mounted on an injection bar I! disposed across the press between blocks H. The injection bar is secured to the upper end of an injection ram l 8 entering a pressure cylinder l9 formed within main ram l3 and open to the pressure of main cylinder [4 through an aperture 20 in the main ram. Thus sumcient pressure applied to injection ram l8 will lift injection bar l1 and injection plunger Hi from the retracted position in die section I (Fig. 1) wherein the bar I! rests. on platen l2, to the operative position shown in Fig. 2.

Two similar auxiliary double acting ram rods 2|, 2| are disposed centrally on either side of the press, and each comprises an upper ram 22 entering a cylinder 23 in head 4, and a lower ram 24 entering a cylinder 25 in base 3. About its mid-length each rod has a reduced section 26 which passes freely through bores in the sides of platen l2 and injection bar l1, terminating in a shoulder 21 above bar l1 and a shoulder 28 below platen I2. The auxiliary ram rods 2| are employed for the initial closing of the die, and for the opening thereof, as explained hereunder.

The operation of the press is as follows:

With the die in the open position shown in Fig. 1, ram rods 26 are in down position with shoulders 21 resting on injection bar I! which in turn rests on platen l2. Rams I3 and I8 are in the retracted position. The moulding powder charge 29 is dropped into the bore I5 of the die section 1.

Hydraulic pressure is admitted to cylinders 25 of the auxiliary rams, and rods 2| rise and move freely through platen l2 and injection bar 21, until their shoulders 28 engage under platen l2, leaving a free length of their reduced sections 26 above injection bar I 1. Continued upward movement of rods 2| lifts the platen l2, and with it the main ram l3, and also the die and injection assembly comprising blocks II, II, die base l0,

die section I, and injection bar I! with attached injection plunger I6. It should be noted that this upward movement of the platen I2, to bring the die section I to closed position against die section B, does not cause any movement of the (retracted) injection plunger I 6 in die section I.

When the die sections have been closed, or substantially so, hydraulic pressure is (automatically) admitted to cylinder I4 of the main ram I3, and hence by aperture 20 to cylinder I9 of the injection ram I8. Owing to the greater surface area of main ram I3 in comparison with injection ram I8, the main ram will be the first affected by this pressure, and it will move to close (if necessary) and seal the die sections, and on the instant that such closure has been fully effected the pressure will cause the injection ram I8 to rise in ram 13 to the position shown in Fig. 2. Elevation of the injection ram lifts injection bar I! and elevates plunger I 6 in die section I to inject the charge 29 into the mould cavity and so form the moulding. During this injection movement injection bar I! slides freely on the reduced sections 26 of ram rods 2|, and it is elevated between spaced blocks II, II supporting the die.

The die is opened, after the moulding operation, by release of pressure from cylinders l4, I9 and 25, and the application of pressure to the upper auxiliary cylinders 23. The resultant downward movement of ram rods 2| causes their shoulders 27 to engage the injection bar I! and force it downwardly to contact platen I2, thereby retracting injection plunger I6 in die section I, after which the bar I! forces the platen I2 downwardly, returning the whole press to the open position shown in Fig. 1, ready for the next moulding.

The drawings and the foregoing description are of a preferred embodiment for simple trans- 4 fer plastic mouldings, and the invention is not 4 limited to such embodiment, but is defined by the appended claim.

I claim:

A moulding press for transfer moulding comprising a fixed die section, a reciprocable die section capable of movement to and from closed relationship with the fixed die section, a platen carrying the reciprocable die section, a main hydraulic ram adapted to close the die sections and hold them in closed relation during injection of the charge, an hydraulic injection ram of smaller area than and disposed within the main ram and subject to the same hydraulic pressure as the main ram, an injection plunger carried by the injection ram, a bar attached to the injection ram and plunger assembly and overlying the die platen, an hydraulic double-acting auxiliary ram passing freely through the die platen and the injection bar, an abutment on the auxiliary ram below the die platen and adapted to move the die sections into closed relation, an abutment on the auxiliary ram above the injection bar and adapted to retract the injection plunger and move the die sections into open relation, and a clearance space between said abutments to permit relative movement of the injection bar away from the platen during operative movement of the injection plunger.

HERBERT WILLIAM DALTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,410,909 Tucker Nov. 12, 1946 FOREIGN PATENTS Number Country Date 687,432 Germany Jan. 29, 1940 

